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Concentration of Risk and Enterprise Wide Disclosures (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Concentration Risk [Line Items]                      
Contract revenues $ 99,211 $ 125,073 $ 159,767 $ 136,843 $ 162,214 $ 140,162 $ 137,420 $ 138,757 $ 520,894 $ 578,553 $ 578,236
Foreign                      
Concentration Risk [Line Items]                      
Contract revenues, percent                 2.30% 1.60% 1.30%
Customer concentration risk | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 108,375       124,142       $ 108,375 $ 124,142  
Concentration risk, percentage                 100.00% 100.00%  
Customer concentration risk | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 100.00% 100.00% 100.00%
Contract revenues                 $ 520,894 $ 578,553 $ 578,236
Customer concentration risk | Federal Government | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 2,319       3,509       $ 2,319 $ 3,509  
Concentration risk, percentage                 2.00% 3.00%  
Customer concentration risk | Federal Government | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 8.00% 11.00% 7.00%
Contract revenues                 $ 42,143 $ 63,823 $ 40,361
Customer concentration risk | State Governments | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 916       4,503       $ 916 $ 4,503  
Concentration risk, percentage                 1.00% 3.00%  
Customer concentration risk | State Governments | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 6.00% 7.00% 7.00%
Contract revenues                 $ 30,470 $ 42,613 $ 37,700
Customer concentration risk | Local Governments | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables 30,187       18,256       $ 30,187 $ 18,256  
Concentration risk, percentage                 28.00% 15.00%  
Customer concentration risk | Local Governments | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 21.00% 16.00% 16.00%
Contract revenues                 $ 107,478 $ 91,591 $ 94,461
Customer concentration risk | Private Companies | Trade and contract retainage receivables                      
Concentration Risk [Line Items]                      
Trade and retainage receivables $ 74,953       $ 97,874       $ 74,953 $ 97,874  
Concentration risk, percentage                 69.00% 79.00%  
Customer concentration risk | Private Companies | Contract revenues                      
Concentration Risk [Line Items]                      
Concentration risk, percentage                 65.00% 66.00% 70.00%
Contract revenues                 $ 340,803 $ 380,526 $ 405,714